Cooks want to tell you grilling is an art or a craft. We know better. Grilling, like anything worth doing, is a science. Anything that has been around for a million years is a science and fire has been considered by millenia as the thing that put humans on the map so nothing is more fundamental to anthropology, evolution and archeology than man, meat and fire.
But science is not always simple and that is why some think they can't grill so they have to call it an art instead. Grilling is easy when you have a science mentality. You just need to quantify it. If you're new to grilling there are some obvious things to do, like control the variables. In the case of meat, for example, make the pieces as uniform as possible when you are new. And if you aren't cooking meat, why are you reading this article?(1) Otherwise, it really doesn't matter how much art you have in you, and you don't need temperature gauges or manuals, just some basic knowledge.
In grilling, chemistry makes biology better
Meat is muscle from delicious animals and is about 75% water, 20% protein, and 5% fat and carbohydrates. Each muscle cell has filaments made of two proteins: actin and myosin.
Meat proteins are made up of amino acids which may be charged and adding salt ions can increase the water-holding capacity of your non-vegetarian treats. The salt moves into the meat and extra water is also absorbed so on your grill the meat holds on to the moisture, which means you get juicier stuff. Yep, it's plain old osmosis, lower concentration to higher through a semipermeable membrane. In meat, this is the plasma membrane that surrounds the individual cells.
Basically, the individual protein molecules in raw meat are in coils and when meat is heated, the bonds break and the protein molecule unwinds. Heat will also shrink the muscle fibers as water is squeezed out and the protein molecules recombine so a brine will help reduce that.
Meat fibers before and after cooking. Micrograph images courtesy Nutrition and Food Management, Oregon State University
Give it a try. Make a salt brine, one cup of salt per gallon of water, and soak some chicken in it for a few hours. Worried about too much salt? Don't be. I am not sure you can oversalt meat before cooking, and I have really tried. And I rarely salt my food post-cooking so it isn't like I have a taste for it.
Gas versus charcoal - it's all physics
There are elitists in science, in tea houses and in grilling. Elitists in grilling will insist charcoal(2) is superior, and can even identify various types of wood. I can't dispute that because if you are the Joe DiMaggio of grilling you might be able to consistently tell the difference but with identical cuts and recipes most people cannot tell. Part of it is showmanship. If you are hanging out with people and you want to talk, go charcoal. For just the family, use the grill.
Some purists prefer charcoal because you can move the heat pretty easily but I have a four-burner grill so that isn't a problem. If you are buying a grill, getting something with 2 or more burners gives you a lot more flexibility.
Direct versus indirect heat
There are only two things to keep in mind with grilling; time and type of heat. Both of those things have a rule of thumb based on meat. For ribs and roasts, as an example, you need to use indirect heat because they will cook slowly but for hamburgers you want direct heat.
Who does it matter? In science, it's the Maillard reaction, after the French physician and chemist Louis Camille Maillard, who discovered the link when he heated sugars and amino acids together and the mixture slowly turned brown. but it's just called browning to grillmasters (3). Chemically, the denatured proteins on the surface of the meat recombine with the sugars present during cooking. When you grill, the outside temperature is higher than the inside, triggering the Maillard reaction and creating stronger flavors on the surface.
It also reaffirms why brining will help you get a better flavor - in brining, the meat's cell fluids are less concentrated than the salt water so water flows out of the meat cells and salt flows in. The salt then dissolves the fiber proteins and the meat's cell fluids become more concentrated, drawing water back in. With more salt and water in the cells, when the meat is cooked and water is squeezed out, there is still water left because water was added before cooking.
You may note by now that I don't get into fat here though it is essential in flavor but there are 600 components in just the aroma of beef alone so getting into fat and figuring out fat levels from animal to animal and then part to part would be too much for a rule of thumb. What is not essential for grilling but interesting to know is that the flavor-carrying molecules in meat are hydrophobic - repelled by water. And meat is 75% water but flavor-carrying molecules dissolve in fat and when that fat is heated, it melts and 'lubricates' the muscle fibers in the meat, helping to keep it juicy. So you use that to your benefit here even without us getting too far into it.
Cooking times - the short version
Make sure your grill is hot. You don't need anything more than your hand. If you can't hold your hand over the grill for more than two seconds, it is hot, around 450 degrees. If you can last 5 to 6 seconds, the grill is about 250 degrees.
If you are cooking some things with indirect heat, move the coals to one side of the grill and cover it or shut off a burner in one side of the grill and cover it. Using the handy times below it is easy to plan so that all of the meat is finished together.
For hamburgers, if you have no timer, you need about 5 minutes on each side over direct heat, as hot as you want. How long is that? If a football game is on, and it's not the last two minutes, that will be 6 plays and a commercial break and you can adjust those ratios accordingly for other things below. If you have a timer, set it to 4.5 minutes for each side. If you have some Pabst Blue Ribbon laying around, pour a little on your personal burger.
For kabobs, 10-12 minutes total, depending on how well done you like the meat. If you have some Pabst Blue Ribbon laying around, pour a little on your personal kabob.
For decent sized steaks, 8 - 14 minutes for medium rare, 12 - 18 minutes for medium. As above, you flip once. If you have some Pabst Blue Ribbon laying around, pour a little on your personal steak. If your steaks still have a bone in, subtract one minute.
For hot dogs, 8 minutes, but you can turn them as often as you want while you drink that Pabst Blue Ribbon. Sausages too, but cook them in a skillet in that PBR first, then finish them on the grill. Dogs and sausages are great for the social aspects of grilling because it gives you something to do with your hands while you discuss Euclidean geometry.
Chicken breasts without the bone are pretty quick but the temperature you use for steaks and burgers will be too high, so here you might want to go indirect if you are also cooking burgers. 8 - 12 minutes, turning once, and juice will run clear when they are ready.
Kim also likes it when I use any old chicken legs with some olive oil on the surface and a rub or salt applied and I cook them for 25 minutes on each side using indirect heat. You can cook those in 35 minutes total if you like but they won't be as awesome as mine.
Ribs are 1-1/2 to 2 hours over indirect heat. Baste with any tomato-based recipe you like, almost anything sweet will make you happy, but only during the last 20 minutes, no matter what you read elsewhere, unless you know what you are doing. Waiting until near the end adds flavor and will keep the sauce from burning.
Barbecue sauce from stuff you have laying around:
1/3 cup soy sauce
1/2 cup water
Small amount of onions and garlic or onion and garlic powder
1/4 cup ketchup
1/4 cup corn syrup
1/4 cup honey
A teaspoon of liquid hickory smoke seasoning if you have it, and then you can tell people you made sweet hickory barbecue sauce for them.
Did I miss anything? If I am wrong on the Internet, I am sure someone will let me know.
(1) And why do you make Veggie Burgers that taste like hamburgers if you dislike meat?
(2) They certainly have history on their side. Where charcoal was invented is something of a science mystery. It's been used for at least 5,000 years but no site can establish a significantly significant first use. Favorites are hickory, cherry, and mesquite.
(3) The Maillard reaction is also what makes self-tanning products work. If that doesn't creep you out, I don't know what will.
The Science Of Grilling